A prior art coupling apparatus for attaching a tool holder to a machine spindle of a type widely used in the industry is depicted in FIG. 3. As can be clearly seen from FIG. 3, there is a gap or spacing 20 of about xe2x85x9 to xc2xc inch between the free end 21 of machine spindle 22 and the integral collar 23 formed on the shank of the tool holder 24. It has been found that this gap or spacing 20 is an area of weakened structural support, particularly when operating the machine at high speeds and when milling or grinding the harder materials. This contributes to misalignment of the tool, tending to provide rough and/or inaccurate work and to cause bending and wearing of the associated tool. Tool holders mounted on a machine spindle and forming a gap between the tool holder collar and the spindle are shown in U.S. Pat. No. 5,407,308. Also, U.S. Pat. Nos. 4,714,389 and 5,352,073 show tool holder apparatus including a means for affixing the tool holder to the spindle for eliminating the gap or spacing; however the tool holder shown in the latter two patents is complex, and the support collar shown therein is integral to the shank, and is not adjustable. As seen from FIG. 1, the present invention discloses tool holder apparatus having an adjustable support collar on the tool holder for eliminating the gap or spacing between the support collar and the end of the spindle thereby enabling the apparatus to be universally employed with varing types and sizes of spindles and tool holders; further the inventive apparatus can be retrofitted to existing equipment.
It is a primary purpose and feature of the present invention to provide a tool holder apparatus which is readily adjustable to provide a solid, stable support for an associated tool, and which adjustable tool holder apparatus eliminates the gap or spacing between the end of a machine spindle, and the support collar on the shank of the tool holder.